Back to EveryPatent.com
United States Patent |
6,018,975
|
Frigerio
|
February 1, 2000
|
Multipass wiredrawing machine with wire tension control device
Abstract
A multipass wiredrawing machine, particularly for drawing metal wires,
comprising a plurality of traction drums for the wire that exits from a
corresponding die, the drums being arranged mutually in succession in
order to wind the wire that exits from the die and guide it on to the next
die. Each traction drum is fixed with respect to the corresponding die and
can move towards or away from the next die; the movement of the traction
drum and of the corresponding die allows constant adjustment of the
tension of the wire between the die and the drum and between the drum and
the next die.
Inventors:
|
Frigerio; Marco (Via Roma, 27, 23827, Lierna, (Prov. of Lecco), IT)
|
Appl. No.:
|
158084 |
Filed:
|
September 22, 1998 |
Foreign Application Priority Data
| Sep 26, 1997[IT] | MI97A2197 |
Current U.S. Class: |
72/280; 72/289 |
Intern'l Class: |
B21C 001/10 |
Field of Search: |
72/280,279,282,289
|
References Cited
U.S. Patent Documents
3812702 | May., 1974 | Benteler | 72/283.
|
4754633 | Jul., 1988 | Glover | 72/288.
|
Foreign Patent Documents |
1681994 | Oct., 1991 | SU | 72/289.
|
Primary Examiner: Crane; Daniel C.
Attorney, Agent or Firm: Modiano; Guido, Josif; Albert
Claims
What is claimed is:
1. A multipass wiredrawing machine, particularly for drawing metal wires,
comprising mounted on a frame thereof: a plurality of dies; a plurality of
traction drums for traction of wire that exits from a respective die, said
drums being arranged in succession in order to wind each one the wire that
exits from the respective die and to further guide the wire on to a next
die, each said traction drum being fixed with respect to a corresponding
said die and each drum and corresponding die being movable with respect to
a next drum and corresponding die so as to be movable toward and away from
the next die; and adjustment means for providing movement of each said
traction drum and corresponding die with constant adjustment of wire
tension between the respective die and drum and between the respective
drum and the next die.
2. The multipass wiredrawing machine of claim 1, wherein said traction drum
comprises a cylindrical body which is rotatable about an axis thereof and
is supported by said frame of said wiredrawing machine, said rotatable
body being movable about a reference midpoint.
3. The wiredrawing machine of claim 2, wherein said traction drum, together
with the corresponding die, are transversely movable with respect to said
traction drum axis, to adjust the tension of the wire being drawn.
4. The wiredrawing machine of claim 2, wherein said traction drum, together
with the corresponding die, are movable in a pendulum-like fashion about
said traction drum axis so as to provide an oscillating motion for
adjusting the tension of the wire that is fed into the next die.
5. The wiredrawing machine of claim 2, comprising guiding elements provided
at said frame, the cylindrical body of said traction drum being guidingly
supported by said guiding elements.
6. The wiredrawing machine of claim 2, comprising pivot means provided at
said frame, the cylindrical body of each said traction drum being
supported by a respective said pivot.
7. The wiredrawing machine of claim 1, comprising detection means for
detecting a position of each of said drum, said detection means being
adapted to actuate said adjustment means for adjusting a rotation rate of
said drum as a function of a detected position.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a multipass wiredrawing machine provided
with a device for adjusting and controlling the tension of the wire being
drawn, particularly suitable for drawing metal wires and the like.
In particular, the invention relates to multiple soap and wet wiredrawing
machines.
The term "wiredrawing" refers to a form of plastic cold working consisting
in the forced passage of the material through the shaped bore of a die,
performed by pulling. The series arrangement of multiple dies with holes
having progressively decreasing diameters allows to reduce the initial
diameter to the selected size.
In order to draw metal wires the wire passes through a die, where its
cross-section is reduced by plastic deformation.
Traction is applied by a traction drum which is located downstream of the
die and, by rotating, winds up a certain number of turns of the wire.
In the case of multipass wiredrawing machines, this operation is repeated
several times in succession, guiding the wire towards the subsequent
stage; accordingly, multiple dies are provided and arranged mutually in
series, and each die has a corresponding drum arranged downstream.
The wire is thus guided from one drum to the next die, with a consequent
reduction in diameter between one pass and the next.
Traction must be applied because the wire being drawn, by causing friction
against the traction drum, which is driven by an electric motor, allows
said drum to pull it (with a capstan-like effect), wind it and then guide
it on to the next drum.
Since wiredrawing occurs without removing material, i.e., with a constant
volume, the ratio between the cross-section and the speed of the wire
becomes particularly important and must be kept constant for each pass
through the different dies and respective drums.
Accordingly, every time the wire diameter decreases, the wire becomes
longer and therefore each drum has a progressively faster rotation rate in
order to wind an increasingly longer wire.
The ideal situation would be one in which the wire passes directly from one
drum to the next, without interposed wire tension control elements which,
by acting directly on the wire, may damage it.
The basic requirement for correct operation is that the rotation rate of
the individual drums must strictly match the tension changes of the wire
as it leaves the respective dies, adapting to the elongations that the
wire is subjected to as it passes through the various dies.
In practice, this theoretically ideal condition is difficult to achieve
because it is difficult to precisely control the speeds of the individual
motors that drive the drums and because of the variables that come into
play during drawing, such as die wear etcetera.
In order to obviate these drawbacks, wiredrawing machines which accumulate
wire between one drum and the next and, more recently, dancer-roll or
bend-detector machines have been used.
These last devices are moving elements onto which the wire being drawn is
guided. Any variations in the elongation of the wire produce angular or
linear movements of these elements which, through position transducers,
such as inductive transducers (potentiometers, encoders, etcetera) control
and correct the speed of the corresponding motor, thus maintaining
continuous drawing.
Conventional solutions described above, however, have the drawback that
they bend the wire around the moving elements, causing bending which is
sometimes excessive if obtaining optimum metallurgical characteristics for
said wire is sought.
Moreover, drawbacks due to the constructive difficulties of wiredrawing
machines using these solutions and difficulties in threading the machines
are present.
Another solution that has been adopted recently to provide wiredrawing
machines whose operation complies as much as possible with the
above-described optimum condition entails controlling the speed of the
individual drums by detecting wire tension changes both in the portion
between the die and the drum and in the portion between the drum and the
following die.
The position of the drums and of the dies is fixed; accordingly, since no
moving parts are provided, control of the speed of the drum motors
generates variable tensions on the wire in the portion between the drum
and the next die.
Another problem that is encountered with wiredrawing machines relates to
the fact that very often, due to malfunctions or to production
requirements, it is necessary to exclude one or more passes of the wire
through the die.
In current machines it is relatively easy to exclude a unit by acting on
appropriately provided controls provided on the control console of the
apparatus. In practical operation, the wire is guided onto the drum that
follows the excluded drum, which remains motionless. In the case of a
linear wiredrawing machine, without dancer rolls or bend detectors, one or
more guiding rolls, fitted in a suitable position, are often used in order
to prevent the wire from sliding against the excluded drum. Due to
assembly and positioning requirements, the diameter of these rolls must be
limited; accordingly, this fact entails negative aspects which affect the
quality of the resulting product.
In fact, it has been observed that any contact of the wire with other
elements that change its orientation produces a relative sliding which
alters the layer of lubricant, i.e., stearate, on the surface of the wire,
consequently varying its intrinsic characteristics.
The smaller the guiding roll or rolls used, the greater this problem
becomes.
SUMMARY OF THE INVENTION
The aim of the present invention is to provide a multipass wiredrawing
machine provided with a device for adjusting and controlling the wire
being drawn, which allows to maintain direct traction of the wire without
having to resort to devices for accumulating said wire or to dancer rolls
and the like or in any case to elements for detecting the tension of the
wire which must be in contact with said wire.
Within the scope of this aim, an object of the present invention is to
provide a multipass wiredrawing machine having a wire traction adjustment
and control device which allows to maintain constant tension on the wire
in the critical pulling portion between the die and the traction drum and
in the critical release portion between the drum and the next die.
Another object of the present invention is to provide a multipass
wiredrawing machine which allows to draw wires made of different materials
with the same machine.
Another object of the present invention is to provide a multipass
wiredrawing machine which has a minimal number of components.
Another object of the present invention is to provide a multipass
wiredrawing machine which is highly reliable, relatively easy to provide
and at competitive costs.
This aim, these objects and others which will become apparent hereinafter
are achieved by a multipass wiredrawing machine, particularly for drawing
metal wires, which comprises a plurality of traction drums for the wire
that exits from a corresponding die, said drums being arranged mutually in
succession in order to wind the wire that exits from the die and guide it
on to the next die, characterized in that each traction drum is fixed with
respect to the corresponding die and can move towards or away from the
next die, the movement of the traction drum and of the corresponding die
allowing constant adjustment of the tension of the wire between the die
and the drum and between the drum and the next die.
BRIEF DESCRIPTION OF THE DRAWINGS
Further characteristics and advantages of the present invention will become
apparent from the following detailed description of a preferred but not
exclusive embodiment of the multipass wiredrawing machine according to the
invention, illustrated only by way of non-limitative example in the
accompanying drawings, wherein:
FIG. 1 is a schematic front view of the multipass wiredrawing machine
according to the present invention;
FIG. 2 is a schematic front view of a first embodiment of the multipass
wiredrawing machine according to the present invention;
FIG. 3 is a schematic front view of a second embodiment of the multipass
wiredrawing machine according to the present invention;
FIG. 4 is a view of an example of transmission between the drum actuation
motor and the drum itself, in the wiredrawing machine according to the
invention;
FIG. 5 is a view of a unit for moving the traction drum;
FIG. 6 is a schematic plan view of the die, illustrating the die shifting
element;
FIG. 7 is a sectional view, taken along the plane VII--VII of FIG. 6;
FIG. 8 is a sectional view, taken along the plane VIII--VIII of FIG. 7.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A first embodiment of the multipass wiredrawing machine according to the
present invention is illustrated with reference to FIGS. 1 and 2 and
comprises a plurality of dies 1, each of which is supported by a
supporting frame 2 whereon a traction drum 3 is provided which is
constituted by a cylindrical body which can rotate about a central axis 0.
The frame 2, as shown in FIG. 2, is supported by means of straight guides
4 by the fixed frame (not shown) of the wiredrawing machine according to
the invention. The cylindrical body drum 3 is thus capable of moving
transversely with respect to the central point 0 by moving along the
guides 4.
The straight guides 4 can of course be replaced with similar systems which
allow a transverse movement of the body 3 with respect to the central axis
0.
FIG. 3 illustrates a second embodiment of the wiredrawing machine according
to the present invention, wherein, differently from the first embodiment,
the frame 2 is supported by means of bearings 5 for connection to the
fixed frame (not shown) of the wiredrawing machine, allowing the traction
drum 3 and the corresponding die 1, rigidly coupled thereto, to perform an
oscillating or pendulum-like movement, moving the unit constituted by the
drum and the die.
For both of the above-described embodiments there are provided different
possible systems for transmitting the motion from the electric motor (not
shown) of the traction drum to the drum itself, according to the speed and
traction force that the drum 3 must apply.
In particular, and by way of example, the following types of transmission
are possible:
direct drive between the motor and the drum;
drive using trapezoidal or toothed belts between the motor and the drum;
drive using a gear reduction unit between the motor and the drum;
mixed drive using a gear reduction unit and trapezoidal or toothed belts
between the motor and the drum and the reduction unit.
As an alternative, it is possible to use, as device for final transmission
to the drum 3, a universal-joint drive which transmits exclusively a
torque but no transverse stress to the drum, making the position of the
drum 3 entirely neutral.
FIG. 4 is a schematic view of an example of transmission between the motor
and the drum in which trapezoidal or toothed belts are used. The reference
numeral 7 designates the drum actuation motor and the reference numeral 8
designates a tensioner for the transmission belt.
The drum shown in FIG. 4 is of the type with a pendulum-like motion and is
supported by the pivot 5.
For both of the above-described embodiments, the movement of the entire
unit constituted by the traction drum 3 and by the corresponding die
activates a position sensor 6, which is conveniently constituted for
example by an inductive transducer, a potentiometer, a proximity sensor,
an encoder, etcetera, and acts on the control elements of the motor 7 of
the drum 3, adjusting its rotation rate.
With reference to the above figures, the operation of the wiredrawing
machine according to the invention is as follows.
With reference in particular to FIG. 1, the reference numeral 10 designates
the wire being drawn, which passes through the die 1 and is wound onto the
cylindrical body of the traction drum 3.
V1 designates the speed of the wire 10 in the portion between the die 1 and
the drum 2 and V1' designates the speed of the wire 10 in the portion
between the traction drum 2 and the next die 1.
The respective speeds V2, V2', V3, V3' and V4 are designated in the same
manner for the subsequent drums 2.
The following conditions must occur in order to achieve correct operation
of the wiredrawing machine:
at the speed V, the tension between the die 1 and the drum 3 must remain
constant;
in the portion between the drum 3 and the next die 1, the speed V' must be
equal to the speed V in the preceding portion.
In order to maintain constant tension of the wire 10 in all of the portions
of the wiredrawing machine, a traction drum must be synchronized with the
preceding traction drum and with the traction drum that follows, so as to
have no variations in the speeds V and V' (where V and V' designate the
speeds, for a generic drum, in the portions before and after the drum,
respectively).
The synchronization speed is assuredly maintained, so that the various
drums 3 remain at the middle position 0, through the lateral movement of
the generic drum 3 towards or away from the drum 3 that precedes it (i.e.,
in one direction or the other with respect to the midpoint 0, which is the
reference point for the synchronization speed).
The movement of the drum 3 activates, by means of the detection means 6, a
signal which, by acting on adjustment means (not shown) of the motor 7,
adjust its rotation rate, restoring synchronization among the various
traction drums 3 and accordingly returning the drum at the midpoint 0.
Means which allow to move the drum 3 when it is necessary to exclude a
drum-die unit are described with reference to FIGS. 5 to 8.
Said means are constituted by an eccentric element 20 which is placed on
the supporting shaft or pivot 5 of the frame 2. The pivot 5 is connected
to an arm 21 which can be placed in two mutually diametrically opposite
positions so as to produce a translatory motion of the peripheral region
of the traction drum 3, thus avoiding contact with the wire which must
bypass the excluded drum.
The die unit is moved upward simultaneously with the downward translatory
motion of the drum and in any case remains connected to the frame 2 at all
times, avoiding any uncoupling and disassembly.
These maneuvers are performed very quickly and without particular equipment
since the die, again designated by the reference numeral 1, is connected
by means of vertical dovetail guiding elements 23 whereon an actuation
pivot 24 is provided which allows to perform the translatory motion and
the consequent disengagement.
In practice, it has been observed that the wiredrawing machine according to
the invention fully achieves the intended aim, since it allows to achieve
constant adjustment of the tension between the die and the drum and the
next die without the aid of dancer rolls or sensors or similar systems for
detecting variations in wire tension.
The wiredrawing machine thus conceived is susceptible of numerous
modifications and variations, all of which are within the scope of the
inventive concept.
All the details may also be replaced with other technically equivalent
elements. Thus, for example, the various figures illustrate a multipass
wiredrawing machine with drums having a horizontal axis: however, it is
also possible to use drums having a vertical axis, stacked horizontal
drums, vertical drums arranged in a step-like configuration, etcetera.
In practice, the materials employed, so long as they are compatible with
the specific use, as well as the dimensions, may be any according to
requirements and to the state of the art.
The disclosures in Italian Patent Application No. MI97A002197 from which
this application claims priority are incorporated herein by reference.
Top